Stabilization of solutions containing peroxygen compounds



United States Patent STABILIZATION OF SOLUTIONS CONTAINING PEROXYGENCOMPOUNDS Oliver S. Sprout, Jr., North Hills, Pa., assignor to PennsaltChemicals Corporation, Philadelphia, Pa., a corporation of PennsylvaniaNo Drawing. Application February 1, 1955 Serial No. 485,620

6 Claims. (Cl. 252-186) This invention relates to the stabilization ofsolutions containing peroxygen compounds, such as hydrogen peroxide andsodium peroxide, which may be used for the bleaching of textile fibersand fabrics, wood, wood pulp, feathers, and the like.

Bleaching solutions containing hydrogen peroxide are inherently unstableunder the normal hot alkaline conditions of usage, and many stabilizingagents have been proposed in an effort to overcome excessivedecomposition of the peroxide.

The present invention includes a stabilizer additive for .a solutioncontaining an inorganic peroxygen compound such as hydrogen peroxideorsodium peroxide and an alkali-metal silicate, comprising a compoundwhich liberates magnesium ions in alkaline aqueous solution and analkali-metal phosphate. Also contemplated by the invention are bleachingbaths stabilized by magnesium ion, alkali-metal phosphate andalkali-metal silicate, and methods of bleaching in which these materialsare employed.

In accordance with the present invention, textile fibers and fabrics,feathers, wood, and wood pulp, for example, may be bleached attemperatures as high as the boiling point of the bleaching bath, and maybe bleached under superatmospheric pressure if desired. Highly bleachedproducts are produced in less time than by conventional processes whileconsuming small, economically attractive, quantities of peroxide.

The bleaching of cotton, silk, and synthetic fabrics has been generallyaccomplished heretofore by the employment of bleaching baths containingabout 0.15 to 3.0%

hydrogen peroxide (100% basis) by weight of solution.

However, it has been found that up to 7% hydrogen peroxide (100% basis)may be required to bleach single strand regenerated cellulose filaments,such as viscose rayon; at ISO-160 F. in a continuous process where thebleaching stage is limited to about 30 seconds. The bleaching bathstabilizing materials of the invention can be used to stabilize bathscontaining up to about 7% hydrogen peroxide (100% basis) equivalent to70 parts per liter or 2333 parts per 33.333 liters or higher, asrequired for viscose filament bleaching. Thus, it has been found that asolution containing 1.5% hydrogen peroxide (100% basis) can bemaintained at 180 F. for seven hours with no loss of peroxide content,when stabilized according to the invention, and a solution containing3.5% hydrogen peroxide (100% basis) under otherwise identical conditionshas been found to undergo decomposition to the extent of only 17% of theoriginal peroxide content.

Pulp from the groundwood process is often commercially bleached by theuse of peroxide. Sodium or hydrogen peroxide, or their combinations, areemployed as the active bleaching agents, the bleaching solutions alsocontaining sodium silicate and Epsom salts, Sulfuric acid or causticsoda is added to the bleach liquors to obtain the desired degree ofalkalinity.

The alkaline peroxide solutions are also used instead ice ofchlorine-containing oxidants to bleach wood pulps from the chemicalpulping processes. The peroxide bleach is usually included in the finalstages of a multistage bleaching process, or it may be used alone toob-' tain the desired product characteristics. The peroxides also finduse in the bleaching of other fibrous cellulosic' materials from cotton,rags, flax straw, agricultural residues, waste paper, wood, wood chips,and the like.

The stabilizers of the invention are equally applicable to all peroxidesolutions of concentration ranging from a low of about 0.25% to a highof about 7.5% (100% basis) as is disclosed in Tables 1 to 8 below. Thesepercentage figures are equivalent to 2.5 to parts per liter or about toabout 2500 parts of peroxide basis) per 33.333 liters respectively, andto all peroxide bleaching procedures regardless of the material to bebleached, its origin, the sequence of operations, or other variationswithin the broad class of peroxide bleaching.

By use of the stabilizers of the invention, the stability of the abovedescribed peroxide solutions in storage is improved, greatereifectiveness in bleaching action is realized, supplementary chemicalsin bleach baths are significantly reduced or eliminated, and economicadvantages in practical bleaching can be achieved.

The stabilizers of the invention contain specific proportions ofwater-soluble organic or inorganic magnesium salts, alkali-metalpolyphosphate and alkali-metal silicates. Among the magnesium saltswhich may be used are magnesium sulfate, magnesium chloride, magnesiumnitrate, and magnesium acetate either in the hydrated or anhydrous form.For example, magnesium sulfate heptahydrate, commonly known as. Epsomsalts, may be employed, or any partially dehydrated magnesium sulfatecontaining less than 7 molecules of water of hydration per molecule ofsalt. Also, magnesium chloride hexahydrate may be used, or any otherhydrated magnesium chloride having less than 6 molecules of water ofhydration per molecule of salt. "The presence of water of hydration inthe salt molecule is not important and may be compensated for whenmaking up the stabilizer formulation. The substitution of magnesium bycalcium, barium, strontium, zinc, or aluminum has not resulted in anequal reduction of peroxide decomposition. Generally, any source ofmagnesium ions can be employed.

Among the alkali-metal polyphosphates (conveniently referred to aspolyphosphates) which may be employed are sodium tetraphosphate, sodiumpyrophosphate, sodi um tripolyphosphate, sodium hexametaphosphate,potassium tetraphosphate, potassium pyrophosphate, potassiumtripolyphosphate, or potassium hexametaphosphate. All of thesepolyphosphates may be employed on the basis of equivalent phosphoruspentoxide content with equally good results. Tri-sodium orthophosphate,or tri-potas sium orthophosphate may also be employed to impart goodstability to bleaching baths, but an immediate precipitation resultswhich may be objectionable in some applications. Thus as can be seen.from the above, the alkali metal polyphosphates are the preferredphosphate additives.

A variety of silicate compounds available in liquid or solid form andvarying in chemical composition are used in the stabilization actionalong with the magnesium ion and alkali-metal polyphosphate. I prefer touse the soluble alkali-metal silicates which are relatively cheap andreadily available. For textile bleaching, one such silicate is a 42 B.sodium silicate solution having a Na O to SiO ratio of 1 to 2.5.Obviously, other sodium silicates having different Na O to SiO ratiosare equally applicable. A silicate frequently used in pulp bleaching hasa Na O to SiO ratio of l to 3.2.

In order to achieve the superior stabilizing action of my invention, theperoxide solutions being stabilized must contain the three components-amagnesium salt, an alkali-metal phosphate and an alkali-metal silicatein specific proportions. Thus, sufficient magnesium salt must be presentto provide a concentration of at least 0.003% magnesium ion by weight.The 0.003% magnesium ion corresponds to 0.03 parts by weight per literor 1 part for 33.333 liters. This is the concentration of magnesium ionused in Tables 2, 4 and 5. Greater amounts of magnesium salts, ofcourse, can be used subject to the limitation that large amounts ofsolids, where solubilities are exceeded, would be objectionable in mostbleaching operations. Preferably from 1 to 67 parts by weight ofmagnesium ion per 33.333 liters of solution are used, this figurecorresponding to a weight concentration of from 0.003% to 0.20%magnesium ion. For every one part by weight of magnesium ion used, 1 to5 parts of an alkali-metal phosphate must be present. The silicatepreferably may vary from 8 to 1750 parts by weight for every 33.333parts of peroxygen solution being stabilized but concentrations of from8 to 2500 parts by weight of alkali-metal silicate per 33.333 parts byweight solution are useful in my invention.

In some applications, the materials to be bleached may contain water ormoisture which would tend to unduly dilute the bleaching solutions. Forsuch cases, strong feed solutions many times as concentrated as thebleach solution can be prepared and added to the bleach bath. Theproportions of the chemicals in the feed solution are increased tocompensate for any dilution effects on introduction into the bleachsolution. For example, a bleach solution containing 0.27% stabilizingadditive, 0.66% silicate, 0.05% caustic soda, and 0.70% H 0 (100% basis)was prepared by introducing a solution of four times this concentration,i. e., 1.08% stabilizing additive, 2.64% silicate, 0.20% caustic sodaand 2.80% H 0 (100%). The strong feed solution was fed at theappropriate rate into a bleach solution through which wet cloth waspassed, thereby maintaining the composition of the bleach solution atthe level specified above. The bleach solution contained 0.27%stabilizing additive compound of 74% MgSO .3H O and 26% Na P O and wasthus equivalent to 0.027% magnesium. The strong feed solution was fourtimes as concentrated and contained .108% magnesium equivalent to 36parts magnesium ion per 33.333 liters.

It is evident from the above that the overall concentration ofmagnesium, polyphosphate and silicate are critical; and, secondly, thatthe ratio of polyphosphate to magnesium is critical in securing thesuperior stabilizing action of my invention.

The components of the stabilizer composition may he added singly to thebleach bath or they may be added in combination. Since the alkali-metalsilicate frequently used is 42 B. sodium silicate, a liquid, it ispreferred to add this directly to the bleach bath, either before orafter the magnesium salt and polyphosphate addition. The silicate isusually not added to mixtures of magnesium salts and polyphosphates dueto formation of insoluble cement-like silicates.

It is convenient for commercial plant practice to provide the properproportions of magnesium salt and alkali metal polyphosphate by blendingthe respective granular salts in the correct ratio. Such a blendedmixture of magnesium salt and polyphosphate will be referred tohereafter, for convenience, as the stabilizer additive. The stabilizeradditive 18 added to the bleach bath either before or after the additionof the peroxygen compound and silicate.

In batch operation, the stabilizer additive is usually added first tothe water of the bleach solution, followed by the silicate, peroxygencompound and any other supplemental alkali or other material desired.This order is not essential insofar as acheivement of stabilization isconcerned, however, and any other order of adding the stabilizingcomponents can be followed, although the order first described ispreferred. The bleach solution is then ready for use. Where bleachingsolutions are prepared and used continuously, the stabilizer additivecomprising magnesium salt and alkali-metal polyphosphate, the silicateand the peroxygen compound in dilute or concentrated form can be addedconcurrently to form the bleach solution.

It is also advantageous to introduce the magnesium salt and alkali-metalpolyphosphate as a stabilizer additive since the polyphosphatesubstantially prevents the precipitation of the magnesium salt insolutions containing silicate. Thus, if a magnesium salt and silicateare introduced into the same solution, an immediate precipitate occurs.With the stabilizer additive of my invention, however, such precipitatesare not formed in solutions of silicates. This is also a distinctivefeature of the invention. While the exact mode of action is unknown tome, and varies with existing conditions, the polyphosphate appears tocombine with the magnesium salt in a manner to prevent immediatelarge-scale reaction with the silicate. It is thus preferable in mostcases to first dissolve the stabilizer additive in the water of thebleach bath to permit interaction of the magnesium salt andpolyphosphate before introduction of the silicate. For manyapplications, nevertheless, such order of mixing is not essential eventhough the granular stabilizer additive and silicate are added to thebleach solution more or less simultaneously with development of a faintopalescense or turbidity which is not objectionable.

Generally, the stabilizer additive of the invention contains sufficientmagnesium compound to provide about 1 part by weight of magnesium, whichis equivalent to about 5 parts by weight of anhydrous magnesium sulfate,and the equivalent of about 1 part by weight to 5 parts by weight of ananhydrous alkali-metal polyphosphate. The parts by weight of thecomponents employed will be correspondingly increased when hydratedcompounds are used instead of anhydrous compounds. The stabilizeradditive may be formulated as a dry powder in the desired proportions,and then added to the solution to be stabilized, but if a magnesium saltand an alkali-metal polyphosphate, for example magnesium sulfate andsodium tetraphosphate, are mixed together prior to addition to thebleaching bath, a magnesium sulfate having not more than about threemolecules of water of hydration per molecule of salt should be employed,instead of magnesium sulfate heptahydrate, since when magnesium sulfateheptahydrate and sodium tetraphosphate are mixed together the massbegins to set up in a few hours and a solid mass results. However,magnesium sulfate heptahydrate and an alkalimetal polyphosphate, such assodium tetraphosphate, may be combined and stored without agglomerationit the magnesium sulfate heptahydrate is first partially dehydrated andthen milled and blended with the tetraphosphate. A stabilizer additivecontaining about 74% by weight magnesium sulfate trihydrate, and about26% by weight of an alkali-metal polyphosphate, such as sodiumtetraphosphate, has been found to provide ex cellent results in plantusage.

Peroxide solutions for textile fabric or fiber or feather bleaching,stabilized in accordance with the invention may contain, for about each33.333 parts of solution, a maximum of about 2500 parts by weight basis)peroxide compound selected from the group consisting of hydrogen andsodium peroxide the equivalent of about 5 parts by weight of anhydrousmagnesium sulfate or anhydrous magnesium chloride, or an equivalentamount of another magnesium salt, about 1 to 5 parts by weight ofalkali-metal polyphosphate, and about 8 to about 1750 parts by weight ofsodium silicate.

A stabilized peroxide solution for textile fabric or fiber or featherbleaching containing, for example, 100 parts by weight of magnesiumsulfate heptahydrate, or an equivalent amount of another magnesium salt,25 parts sodium tetraphosphate, and 175 parts sodium silicate,corresponding to a concentration of 0.03%, 0.0075% and 0.0525%respectively, by weight of solution has been found ot give excellentresults. The concentration of the stabilizer may be greatly increased ifnecessary as a result of adverse conditions, such as an increase inalkalinity or temperature of the bath. Caustic soda, soda ash, or sodiumsilicate may be added for the purpose of adjusting alkalinity, butsatisfactory bleaching with decreased peroxide consumption has beenelfected at pH values as low as 8 to 9.5. In continuous operations, thebleaching bath composition is maintained substantially constant by theintroduction of feed liquor which replenishes stabilizer and peroxidelost in drag-out.

The bleaching of dark colored feathers by hot stabilized solutions ofhydrogen peroxide produces feathers of a high degree of whiteness, whichis unobtainable by conventional methods. For example, it has been foundthat dark brown goose feathers can be bleached to a full white hue by ableaching procedure in which the feathers are immersed in an aqueousbleaching solution containing hydrogen peroxide, sodium silicate,magnesium salt, and polyphosphate in the proportions of my invention.The feathers are heated generally for several hours in the bleachingsolution, after which the feathers are rinsed and dried.

In pulp bleaching, the peroxide solution should contain sufiicientmagnesium compound to provide about 0.05 to 0.5 part of magnesium per1000 parts of solution, which is equivalent to about 0.25 to 2.5 partsof anhydrous magnesium sulfate per 1000 parts of solution, about 0.05 to2.5 parts of alkali-metal polyphosphate per 1000 parts of solution,maintaining the ratio of phosphate to magnesium at all times within therange of 1:1 to 5:1, and about 1.5 to 100 parts of sodium silicate per1000 parts of solution. A stablizer additive containing a magnesium saltand an alkali-metal polyphosphate, such as, for example, 74% by weightmagnesium sulfate trihydrate and 26% sodium tetraphosphate, may bedissolved in the water making up the bleaching solution followed by thedesired amount of sodium silicate and then the peroxide, after which thebleaching liquor is ready for use. If necessary, an acid or alkali maybe added to the solution to obtain the desired alkalinity. Sodiumperoxide or a mixture of sodium peroxide and hydrogen peroxide isgenerally employed for pulp bleaching. The stabilizing compositions ofthe invention are equally effective for use with hydrogen peroxide,sodium peroxide, or mixtures thereof.

In employing my invention in pulp bleaching, only A water-white,iron-free sodium silicate having a Na O to SiO ratio of 1 to 2.5,containing 36.8% solids, and having a B. gravity of 42 is preferred,when a silicate is used, but silicates of other ratios, such as thathaving a 1 to 3.3 ratio, may also be used.

The invention will be further illustrated by reference to the followingspecific examples:

EXAMPLE 1 A series of experiments were performed to determine the effectof sodium silicate on the stability of hydrogen peroxide solutions.Sodium silicate, such as Philadelphia Quartz Star Brand or equivalent,having a Na O/SiO ratio of 1 to 2.5 is the most commonly used 6.stabilizer in the textile industry. Caustic soda may also be added,primarily to aid bleaching. Silicates are generally used in peroxidebleaching to assist penetration into the fibers and motes, suspenddissolved matter, and act as a detergent. A series of solutionscontaining 0.25% hydrogen peroxide basis), and containing variousquantities of sodium silicate, were maintained at F. for the periods oftime indicated in the table below. The results are as follows:

Table 1 pH H202 decomposition Percent: sodium silicate Expt. No. Percentof original decomposed Time Start End Hrs. Mins.

0.75 1.5 siL. 0.1 NaOI-I...

1 "N silicate (NarO/SiOz ratio 1/3.2) used in this run to determinewhether a ditierent type of silicate would alter results.

It will be observed that the addition of sodium silicate to the peroxidesolutions greatly decreased the stability thereof.

EXAMPLE 2 Table 2 pH H202 decomposition Percent Not P4013 Percent TimeParts 1 Start End original decomposed Hrs. M ins.

1 Based on 0.03% MgSO4.7H2O=1 part, 0.007591, NaoP4On=ll25 part, 0.0525%silicate=L75 parts.

These experiments show that when .0075 to 0.015% of Na P O are added toperoxide solutions containing 0.03% MgSO .7H O and 0.0525 sodiumsilicate effective peroxide stabilization is obtained (Nos. 4, 5 and 6);but that when larger amounts of Na P O are used Without increasing theother components little effective stabilization is obtained (Nos. 1, 2and 3).

EXAMPLE 3 A series of experiments were performed to ascertain the eifectof various combinations of stabilizing ingredients on peroxidestability. The ingredients were added to peroxide solutions containing0.25% by weight hydrogen peroxide 100% basis) and these solutions weremaintained at 180 F. for the periods of time indicated. The results areas follows:

Table 3 pH H2O: decomposition Percent Expt. Solution eonstitucon-Percent Time No. ents) stituof out Start. End original decom- .l'lrs.Mins.

posed 1.-. 112010111 5,0 5.9 72.8 1 2 Sodium sil eatonn 0.0525 10.2 10.299.2 0 20 3 Mg'SO4-7H2O 0.03 6.0 5.0 80.0 2 30 4.- NaePioia 0.0375 8.87.5 76.5 24 i3 5. klfialIzign 8.8075 8.2 7.2 94.3 24 0 1110 4 1:1 375 0nhf p s 8 }7.0 0.0 01.5 24 10 "a- 4 l3 .0075 7 l i gi 8837 }0.8 '3 89.724 0 is 4 1:1 8 Sodium silicatcnu 0.0525 24 (0.03% IMgSO4.7H2O=1 part,0.053751% NaaP4O13=L25 part8, 0.0525% sihcatc =1.75 parts.)

Table 3 shows that the stability of a peroxide solution (No. 1) is quitepoor since major decomposition occurs in an hour at 180 F. Addition ofsodium silicate as indicated actually accelerates decomposition (No. 2),while addition of Epsom salt to a peroxide solution (No. 3) has verylittle stabilizing effect. The stability of peroxide solutionscontaining sodium tetraphosphate in several proportions (Nos. 4 and 5)or sodium tetraphosphate with Epsom salt (Nos. 6 and 7) or silicate (No.8) is somewhat improved since a little peroxide (about 1-40%) remainsafter heatingfor 24 hours. The degree of stabilization achieved is ofsuch a minor degree, however, that these solutions would have no valueas commercial bleach baths. On the other hand, in accordance with myinvention, solutions containing critical proportions of Epsom salt,sodium tetraphosphate and silicate suffered only from about 10% to 50%decomposition, on heating 24 hours at 180 F. as is shown by Table 2,Nos. 4, 5 and 6.

EXAMPLE 4 To ascertain the effect of substituting various phosphates inthe stabilizing formulation, various constituents were added to 0.25% byweight hydrogen peroxide solutions (100% basis) in quantities sufiicientto provide the same quantity of P 0 as would be normally supplied by0.0075% by weight sodium tetraphosphate in solution. All solutionscontained 0.03% by weight magnesium suifate heptahydrate and 0.0525 byweight sodium silicate in addition to the other constituents. Theresults are as follows:

07HzO=i part, 0.00759}; NHOP4013=025 part, 0.0525% sodium silicate=1.75parts.)

Insofar as stability is concerned, any of the above polyphosphates canbe employed with success. It was also found that although the solutionof magnesium sulfate and tri-sodium orthophosphate had excellentstability a precipitate was produced which would be disadvantageous inpractice (No. 4).

8 1 EXAMPLE 5 A series of tests were performed to ascertain the effectof substituting other cations for magnesium ions, and

5 various constituents were added to 0.25% hydrogen peroxide solutions(100% basis) in quantities suflicient to provide an amount of cationchemically equivalent to Mg++ in solutions containing 0.03% by weightmagnesium sulfate heptahydrate. All solutions contained 10 0.0075 byweight sodium tetraphosphate and 0.0525 by weight sodium silicate inaddition to the constituents shown. The results are as follows:

Table 5 pH H202 decomposition Percent Expt. Cation constituent con-Percent Time N o. stituont of Start End original decomposed Hrs. Mins.

lVIgClzfiI-IzO. 0. 2 s. 3 10. 4 24 0 0.5 0.7 08.6 4 25 0.7 as 98.0 a50.7 9.8 98.0 5 45 8.7 7.8 42.0 24 10 7. 1 o. 0 57. s 21 10 0. 4 7. 0 120 2:5 5',

(0.03% MgSO .7I'l2O=l part, 0.00757 N11nl1O ;--0.25 part, 0.0525% sodiumsilicatc=1.75 parts.)

From the above it will be seen that Ca Ba++, Sr++,

Zn++, and Al do not give stability equivalent to Mg, and that magnesiumchloride may replace magnesium sulfate with equivalent efficacy.

EXAMPLE 6 quantities of sodium hydroxides were added to 0.25% by weighthydrogen peroxide solutions (100% basis) containing 0.03% magnesiumsulfate heptahydrate (1 part) and 0.0525% by weight sodium silicate(1.75 parts), the solutions being maintained at 180 F. for the doperiods of t1me 1nd1cated. The results are as follows:

Table 6 5O N3aP40|3 NaOH pH H202 Decomposition Percent Expt. oiOrigi-Time No. Percent Parts Percent Parts Start End nai De- C0111- posed NoneNone None None 9.0 7.8 6.4 23 None None 0.015 0.5 9.9 0.7 14.0 23 550.0075 0.25 0.015 0.5 10.0 9.8 17. 0 21 0 0.015 0.5 0.015 0.5 10.1 9.930.8 23 55 0.0375 1.25 0.015 0.5 10.3 9.9 72.8 23 55 None None 0.03 110.4 10.2 16.0 2:; 55 0.0075 0.25 0. 03 1 10.5 10.3 34.4 24 5 0.015 0.50.03 1 10.4 10.3 00.0 23 55 0.0375 1.25 0.03 1 10.4 10.4 84.0 23 55 NoneNone 0.00 2 10.0 10.8 33.0 24 0 0.0075 0.25 0.00 2 10.0 11.1 72.8 24 50.015 0.5 0.06 2 10.6 10.0 00.4 24 5 0.0375 1.25 0.06 2 10.8 10.8 72.824 0 EXAMPLE 7 A series of experiments were performed in which increasedquantities of stabilizer were used with increased causticconcentrations. The solutions to which the constituents were added were0.'25% by weight hydrogen peroxide solutions (100% basis) maintained at180 F[ The results are as follows:

.those from the hypochlorite bleach. Under the explora tory conditionsemployed in these trials, the use of solutions containing about 3%hydrogen peroxide before the Table 7 MgSOMHgO Sodium silicate NauPtOn PH11202 decomposition Efipt. NaOH, Percent Time percent of Percent PartsPercent Parts Percent Parts Start End original decom- Hrs. Mins.

posed At equal ingredient concentration, use Of 0.25 part sodiumtetraphosphate is superior to 1.25 parts. At a given sodium hydroxidecontent, the use of 0.25 part sodium tetraphosphate permits the use ofreduced amounts of stabilizing chemicals. If the sodium hydroxidecontent of the bath increases, as might happen in use, stabilization maybe controlled to some extent by increasing the stabilizer concentrationat 0.25 part sodium tetraphosphate.

EXAMPLE 8 A series of experiments were performed to determine whethercontinuously generated and processed rayon filaments might .besatisfactorily bleached by the use of hydrogen peroxide instead ofsodium hypochlorite. The filaments are continuously generated and formedinto a loose. yarn which then progresses successively through thefollowing stages: acid, water-wash, sulfide, wash, bleach, acid, wash,soap, and dry. Twenty seconds are normally allowed for bleaching, orabout two inches on the machine.

Peroxide bleaching solution was first used in place of the usualhypochlorite bleach without subsequent washing and soaping. Increaseswere then made in the peroxide. The washing and soaping stages were nextrespectively reintroduced into the cycle. The peroxide bleachingsolution was then added after soaping and before drying with subsequentreductions in strength of the heater gave most satisfactory results. Theinfluence of temperature on the speed of the bleaching reaction is ofconsiderable importance and elevated temperatures perrnit reduction inbleaching time as well as reduction in peroxide content of the bleachsolution. Thus, use of solutions containing 6.6% hydrogen peroxide wasrequired for satisfactory bleaching when washing and soaping wereomitted and the normal machine distance of about two inches forbleaching was lengthened to about fourteen inches including drying (RunNo. 2). However, solution strength requirements were reduced to only3.3% hydrogen peroxide when. the bleach was added after soaping andimmediately before the heater, where warm air at about 180 F. dried theyarn on the last few inches of the machine (Run No. 7).

EXAMPLE 9 A series of plant runs were performed on various types offabrics in which kier-boiled and washed cloth was pulled from a storagepit in succession through a washer,

a saturator filled with hot water, a squeezer, first and second U-shapedtubes containing heated bleach solution, a final squeezer, and out to awasher. The cloth speed was 110 yards per minute through the U-tubeswhile the washers were operated intermittently at 225 yards per minute.pits to the first U-tube, and in one run the second U-tube containedonly a small amount of bleach solution and peroxide bleaching solution.The results are as follows: was operated essentially dry. In anotherseries of Table 8 SUMMARY OF PROCEDURES AND RESULTS FOR CONTINUOUS RAYONYARN BLEAOHING Percent Bleaching Residual Bun Bleaching solutionBleaching solution solution Further process Results H509 No. used addedtemp., operations F. yarn basis 1 0.5% av. OhNaOOl. Bleaching stage...Control .4% H 0. Not as well bleached as No. 1, NaOOl.

do- Alter soap, before heater.

About as good as No. 1, N 21001 White not as good as No. 3.-. Stillpoorer bleach than N o. 4

harsh.

All peroxide bleach solutions contained 0.12% stabilizer additive and0.44% sodium silicate.

The stabilizer additive employed consisted of 74% by weight magnesiumsulfate trihydrate and 26% by weight sodium tetraphosphate. Continuouslyproduced rayon yarn was bleached with stabilized solutions of hydrogenperoxideto-yield products which appeared as white as 7!! follows:

bleaches, the bleaching solution used in one days operation was heldover for use the second day. Feed liquor addition was made to maintainthe peroxide strength of the bleaching solutions in the U'tubes. Theresults are as In two instances passage was directly from the Table 9 ISUMMARY OF BLEACHIN G CONDITIONS AND RESULTS FOR STABILIZED HIGHTEMPERATURE CONTINUOUS PEROX IDE BLEAOHING Cloth Pro-treatment 1stU-tube Single Double Bleach Temp., Time. Type Yards Pounds wash, nowash, soln. F. mins. pH range Feed preheat preheat soln.

4.75 168 40 7.8-8.2 1 1 2.85 163 26 7. 5-8. 3 7 2 4.75 173 40 6. 7-7. 8a 1 4.75 2.85 161 24 8. 0-9. 2 9 3 e2 167 6.8-8.0 3 2.3.? 164 20 7. 8-3.a 1 3 Cloth 2nd U-tube Percent Whiteness H 01 Bleach (100%) houseconwash Acceptance 'lype Yards Pounds Bleach soln. Tom Time, pH Feedsumed 1st U 2nd U F mins. range soln. cloth basis 4.75 yd. None-.Acceptable. 2.85 yd. do 4.75 yd. ..do. Do. 4.75 yd. Do. 2.85 yd. .do..Do. 4.75 yd. Do. 2.85 yd. do Do. 4.75 yd. 8 oz. duck 2.85 yd. jeans None1 Composition of bleach solutions: 1. 0.12% stabilizer additive, 0.22%silicate, 0.25% H20; (100%). 2. 0.12% stabilizer additive, 0.44%silicate, 0.25%

H 0: (100%). 3. Residual liquor from previous days runs-as #2. 4

0.12% stabilizer additive, 0.44% silicate, 0.35% H20 (100 2 7Composition of feed solutions: 1. 0.36% stabilizer additive, 0.66%silicate, 1.16% H10: (100%). 2. 0.36% stabilizer additive 0.66%silicate, 1.58% H10, (100%). 3. 0.36% stabilizer additive, 1.32%silicate, 1.68% H 0, (100%).

The stabilizer additive consisted of 74% by weight stabilizer additive,0.66% by weight sodium silicate,

magnesium sulfate trihydrate, and 26% by weight sodium tetraphosphate.

The pH values of 7-8.5 attained in all the runs were well below thevalues of 10.5, or higher, commonly employed for cotton bleaching andconstitute a distinctive feature of the process.

EXAMPLE 10 tory and was not improved by reducing the temperature of thesteam chamber from about 212 F. to 190 F. A second run using 0.2% NaOHin a similar saturator solution produced worse results than the firstrun.

To provide for more effective stabilization of peroxide during steaming,the stabilizer additive was increased to provide a saturator solutioncontaining 0.18% by weight 0.04% by weight caustic, and 0.70% by weighthydrogen peroxide 100%). Bleaching and mote removal essentiallyequivalent to results from the regular plant procedure were obtained.Better stability was shown by the 40 peroxide content of cloth leavingthe steamer which was about twice as great as from the initial run.

The amount of stabilizer additive was then increased to give stillfurther stabilizing action, the saturator solution containing 0.27% byWeight stabilizer additive, 0.66%

by weight sodium silicate, 0.05% caustic soda, and 0.70% by weighthydrogen peroxide (100%). improved stabilizing action and also presentedan opportunity to reduce the quantity of peroxide in the satu-. ratorsolution for reasons of economy since the residual, peroxide found washigher than necessary. Bleaching and mote removal were at least as goodas by the regular procedure for a variety of cloth including 1.90 and2.35 yards per pound twill, and 2.85 yards per pound jeans. The bleachbeing stabilized in accordance with my invention appeared to impart amore desirable blue-white tint in the bleached goods than the customarypink hue. The results are as follows:

This indicated Table 10 APPLICATION OF STABILIZER ADDITIVEPEROXIDESATURATOR SOLUTION IN CONVEYOR STEAMER Saturator solution PercentPercent H O; Percent Cloth Yards Pounds Stabii- 202 (100%)whiteacceptabilityv izer Addi- Percent Percent (100%) consumed ness tivesilicate caustic cloth basis 2.00 yd./lb. twill Regular 0. 71 Moteremoval acceptable but not completely satisfactory. 0.70 0.46 84.7Bleaching and mote removal unsatisfactory. 0. 0. 51 83. 3 Do. 0. 70 0.46 lleas: equivallentt 1to reglrlar proceidure. h eas equiva en 0 reguar proce ure wit gig ggfigifit: 28g respect to bleaching and moteremoval. Z yd'llb. 2' 384 0. 70 0.81 Blue white tmt Do 6,000 Dn 62 90. 0Acceptable. Poplin-- .70 89.7 Do.

1 Regular silicate content in saturator solution is 0.88% by weight. Allsaturator solutions derived from teed solutions at 400% the saturatorcon centration.

13 It should be noted that in these runs no cooling water was used toreduce the temperature of the cloth coming from the caustic stage hotwater washer into the peroxide 14 It is evident that the most extremedecomposition was exhibited by bleaching solution No. l, which is thetypical mill formula. Solutions 2, 3 and 4, employing the saturator.Saturator temperatures as high as 130 F. stabilizing composition of myinvention, all provided betwere observed. This was in contrast to usualoperations ter stabilization than the commercial solution. The stawherea cold water spray on the cloth is normal pracbility of these solutionsincreased with increased stablizer tice to prevent undue decompositionof the peroxide satadditive (3 and 4). urator solution. Bleach solutionsstabilized in accordance with my invention showed no instability eventhough EXAMPLE 12 operating conditions occasionally necessitated holdingthe Equal weights of semi-bleached. flax pulp were further bath idle forsome time or permitted the entrance of unbleached by treatment withsolutions made up as dedue amounts of alkali. scribed in Example 11.Bleaching was performed at a The normal saturator solution contained0.88% by 5% pulp consistency with oxidant suflicient to provide weightsodium silicate while the largest amount of silithe equivalent of 2%sodium peroxide on the pulp basis. cate used in the system whenstabilized in accordance 5 Bleaching was continued for twenty-threehours at room with my invention amounted to 0.66% silicate or 75%temperature to observe any long-term decomposition cfof that normallyemployed. fects, after which the pulp was warmed to 120 F., held EXAMPLE1 about an additional hour and then washed. The white- A series ofbleach solution compositions were made g fi g g i Peroxide consumpnonare up, one of which was the typical mill formula used in ta u ate mt eta 6 e wood pulp bleaching, and the other three employing my Table 12stabilizer additive consisting of 74% by weight magnesium sulfatetrihydrate and 26% by weight sodium tetraphosphate. These solution werestored at 100 F. and Bleach solution 1 2 3 iit iiii their oxidizingpower was periodically determined. The compositions of the varioussolutions are tabulated in Percent equivalent Nstot consumed- 0.90 1.071.08 the table below in relation to their loss of oxidizingWhlteness(Mgo=100 power with time. (It may be noted that some sulfuricacid was employed in making up these solutions to pro- The yp millfel'lnula (bleach Solution vide the desired free soda to silica ratio;however, with yielded pulp of the lowest whiteness and its actualperoxsome silicates that have a Na O to SiO ratio of 1/3.2, iconsumption s also H the residual the addition of sulfuric acid may notbe required.) peroxide remaining in the p p would be lost in the Theresults are a follow tralization or washing treatments which commonlyfol- Table 11 low peroxide bleaching. The pulps which were bleached withsolutions containing the stabilizer additives of my invention (Nos. 2and 3) had significantly higher white- Bleach solution composition N0Parts/1'00) Parts ness in the products than did the mill formula. For

practical purposes, the peroxide consumption using solu- 1 2 3 4 tionNo. 3 was not appreciably greater than No. 1, especially in View of theincreased whiteness. 26$ 1% ti i %i) MgSO Nos. 0 5 0 5 2 7 Epsomssmtsoinnorit:21:33: 0.5 None None None EXAMPLE 13 57.4 3.25 28.9 17.4 ASeries of experiments Were conducted to test e 3Zl%xiita%?ftt5a;x:::: itat 02 8:2 om of the e i the Hydrogenperoxide,50% 9.8 9.8 9.8 9.8 blhzersfor sodium peroxide solutions 1n bleaching gp ig ggg pg pggegg 3 groundwood-sulfite pulp mixtures. Thestabilizer addiprgsggdsag 1 9 24 718 4 11 6 6 3 tive employed consisted of 74% by weight magnesium 7 g atsuulfate trihydrate and 26% by weight sodium tetraphosphate. The resultsare as follows:

Table 13 Bleaching solution, percent Residual NaaOipH Whiteness Bleachnormal strength Stabilizer number Notes additive Epsom Silicate MinutesPercent Start End Hunter Points Blank salts original increase 1Control..- 100 None 125 10.0 10.3 9.2 75.0 7.4 07.0 0- d 100 50 None 18.0 10. 2 9. 0 74. 0 5. 3 09. a 2 None 50 100 20.0 10.3 9.1 75.5 7.9 07.0None 50 100 13.8 8.7 7.4 72.4 2.9 09.5 (=0. None 50 100 90 13.2 10.4 9.075.4 5.9 09.5 None 50 None 120 19.4 10.0 8.9 75.4 0.1 09.3

1 Solution adjusted to pH 10 by additional amount 2 Solution adjusted tofree alkalinity present in mill 3 Used MgSOtJHgO equal to MgSOt.3HtO1'11 stabilizer additive and substituted NasPao o for NasP O instabilizer additive on basis of equal P405 content.

Normal solution contained (parts/1,000 parts of solution):

14.8 parts sulfuric acid per 1,000 parts of solution.

bleach by use of only 12.5 parts sulfuric acid per 1,000 parts ofsolution.

It will be seen from the above table that when the stabilizer additiveof the invention is employed, it can be substituted for all of the Epsomsalts commonly used in mill bleach formulations, and for one-half of thesodium silicate contained in the regular mill bleach solution. Also, inbleach No. an equivalent weight of magnesium sulfate heptahydrate wassubstituted for magnesium sulfate trihydrate in the stabilizer additiveand sodium tripolyphosphate was substituted for sodium tetraphosphate.The bleaching results produced by this stabilizer additive wereequivalent to those produced using magnesium sulfate trihydrate andsodium tetraphosphate.

EXAMPLE 14 A peroxide feather bleaching bath was made up in whichsufiicient stabilizer additive, containing 74% by weight magnesiumsulfate trihydrate and 26% by weight sodium tetraphosphate, was added to100 gallons of water to produce a solution containing 0.12% by weightstabilizer additive. The stabilizer additive was added as a dry powderand, after it became dissolved, a liquid-type sodium silicate was addedto the bath in an amount equivalent to 3.75 pounds of sodium silicateper 100 gallons of solution, producing a concentration of 0.44% byweight sodium silicate in the solution. The sodium silicate had adensity of 42% B. Containing 10.5% Na O and 26.3% SiO by weight, in aratio of l to 2.5. Hydrogen peroxide was then added to the bath in anamount equivalent to 20.5 pounds of 130 volume strength hydrogenperoxide per 100 gallons of solution, producing a concentration in thebath of 0.86% hydrogen peroxide (100% basis) by weight. The pH of thissolution was 9.7.

The bleach bath was then heated to a temperature of 190 F. and darkbrown goose feathers were added thereto. After ermitting the bath tostand for 65 minutes, the temperature had decreased to 140 F. and the pHto 8.4. The bath was then heated so that after another hour thetemperature had again reached 190 F. At the expiration of an additional20 minutes, no further bleaching was observed.

The feathers were removed from the bleach bath, rinsed in water, anddried by exposure to a moving air stream, followed by storage in an ovenat 140 F. The feathers had lost their original dark brown color and werea satisfactory full white.

A peroxide feather bleaching bath having substantially the samecomposition as that above, except that the stabilizer additive wasomitted, failed to produce significant bleaching of feathers and wasunstable when heated to 120 F.

EXAMPLE A series of bleaching solutions were prepared in order toascertain the effect of the stabilizer additive of the invention on woodbleaching solutions. The solutions were prepared as follows:

Solution No. 1 represents a typical bleach used in the commercialbleaching of mahogany veneer. Solution No. 2 contained a stabilizeradditive of the invention instead of sodium silicate, and solution No. 3employed no caustic soda but contained a stabilizer additive of theinvention and sodium silicate, the latter being employed to supplyalkalinity. The stabilizer additive contained 74% magnesium sulfatetrihydrate and 26% sodium tetraphosphate.

Upon standing a few minutes, solution No. 1 proved so unstable thatviolent bubbling occurred, with the result that most of the solutionboiled out of the container. Only a negligible amount of bubblingoccurred with solutions No. 2 and No. 3, and substantially all theperoxide of these solutions was found to have been retained, uponanalysis of the solutions on the following day. Mahogany veneer bleachedwith solutions No. 1 and No. 2, immediately after preparation of thesolutions and before substantial decomposition of solution No. 1occurred, was bleached equally well, with the bleaching effect ofsolution No. 3 being somewhat inferior.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof and the invention includes all suchmodifications.

This application is a continuation-in-part of my application Serial No.382,217 filed September 24, 1953, now abandoned.

Having thus described my invention, I claim:

1. A stabilized peroxide solution containing for each 33,333 parts ofsolution a maximum of about 2,500 parts by weight basis) of a peroxidecompound selected from the group consisting of hydrogen and sodiumperoxide, about 8 parts to about 2,500 parts by weight of analkali-metal silicate, anhydrous and hydrated magnesium salts selectedfrom the group consisting of magnesium sulfate, magnesium chloride,magnesium nitrate and magnesium acetate in a quantity suificient toprovide at least about 1 to 67 parts by weight of magnesium, and foreach 1 part of magnesium, about 1 part to 5 parts by weight of an alkalimetal polyphosphate.

2. A stabilized peroxide solution containing for each 33,333 parts ofsolution a maximum of about 2,500 parts by weight 100% basis) of aperoxide compound selected from the group consisting of hydrogen andsodium peroxide, about 8 parts to about 2,500 parts by weight ofalkali-metal silicate, anhydrous and hydrated magnesium salts selectedfrom the group consisting of magnesium sulfate, magnesium chloride,magnesium nitrate and magnesium acetate in a quantity sufiicient toprovide 1 to 67 parts by weight of magnesium, and for each 1 part byweight of magnesium about 1 part to 5 parts by weight of a compoundselected from the group consisting of sodium tetraphosphate, sodiumtripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate,potassium tetraphosphate, potassium tripolyphosphate, potassiumpyrophosphate, and potassium hexametaphosphate.

3. A stabilized peroxide solution containing for each 33,333 parts ofsolution a maximum of about 2,500 parts by weight (100% basis) of aperoxide compound selected from the group consisting of hydrogen andsodium peroxide, about 8 parts to about 1,750 parts by weight of sodiumsilicate, about 2.5 parts by weight of sodium tetraphosphate, andanhydrous and hydrated magnesium salts selected from the groupconsisting of magnesium sulfate, magnesium chloride, magnesium nitrateand magnesium acetate in a quantity sufficient to provide about 1 partby weight of magnesium.

4. A stabilized peroxide solution containing for each 33,333 parts ofsolution a maximum of about 2,500 parts by weight (100% basis) of aperoxide compound selected from the group consisting of hydrogen andsodium peroxide, about 8 parts to about 1,750 parts by weight of sodiumsilicate, about 2.5 parts by weight of sodium tripolyphosphate, andanhydrous and hydrated magnesium salts selected from the groupconsisting of magnesium sulfate, magnesium chloride, magnesium nitrateand magnesium acetate in a quantity sufficient to provide about 1 partby weight of magnesium.

5. A stabilized peroxide solution containing for each 33,333 parts ofsolution a maximum of about 2,500 parts by weight (100% basis) of aperoxide compound selected from the group consisting of hydrogen andsodium peroxide, about 8 to 2,500 parts by weight of alkalimetalsilicate, about 1 to 335 parts by weight of an alkali metalpolyphosphate, and anhydrous and hydrated magnesium salts selected fromthe group consisting of magnesium sulfate, magnesium chloride, magnesiumnitrate and magnesium acetate in a quantity suflicient to provide about1 to 67 parts by weight of magnesium while maintaining the ratio ofalkali-metal polyphosphate to magnesium within the range of 1 to 1 to 5to l.

6. A method of bleaching textile fabrics, feathers and wood fiber whichcomprises subjecting the fabrics to the action of a peroxide bathcontaining for each 33,333 parts of solution not in excess of about2,500 parts by weight of hydrogen peroxide (100% basis), about 8 partsto about 2,500 parts by weight of an alkalimetal silicate, anhydrous andhydrated magnesium salts selected from the group consisting of magnesiumsulfate, magnesium chloride, magnesium nitrate and magnesium acetate ina quantity sufficient to provide 1 to 67 parts by weight of magnesiumand, for each 1 part of magnesium, about 1 part to 5 parts by weight ofan alkali metal polyphosphate, while maintaining the pH within the rangeof 7 to 14.

References Cited in the file of this patent UNITED STATES PATENTS1,181,409 Schaidhauf May 2, 1916 1,758,920 Baum May 20, 1930 2,004,809Gilbert et a1. June 11, 1935 2,027,838 Reichert Jan. 14, 1936 2,037,566Durgin Apr. 14, 1936 2,121,952 Colonius June 28, 1938 2,141,189 LindDec. 27, 1938 2,160,391 Reichert et al. May 30, 1939 2,164,146 Reuss etal June 27, 1939 2,191,431 Kautfmann Feb. 20, 1940 2,220,682 Kauffmannet al Nov. 5, 1940 2,333,916 Campbell et al. Nov. 9, 1943 2,366,740McEwen Jan. 9, 1945 2,706,178 Young Apr. 12, 1956

1. A STABILIZED SOLUTION CONTAINING FOR EACH 33,333 PARTS OF SOLUTION AMAXIMUM OF ABOUT 2,500 PARTS BY WEIGHT (100% BASIS) OF A PEROXIDECOMPOUND SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND SODIUMPEROXIODE, ABOUT 8 PARTS TO ABOUT 2,500 PARTS BY WEIGHT OF ANALKALI-METAL SILICATE, ANHYDROUS AND HYDRATED MAGNESIUM SALTS SELECTEDFROM THE GROUP CONSISTING OF MAGNESIUM SULFATE, MAGNESIUM CHLORIDE,MAGNESIUM NITRATE AND MAGNESIUM ACETATE IN A QUANTITY SUFFICIENT TOPROVIDE AT LEAST ABOUT 1 TO 67 PARTS BY WEIGHT OF MAGNESIUM, AND FOREACH 1 PART OF AMGNESIUM, ABOUT 1 PART TO 5 PARTS BY WEIGHT OF AN ALKALIMETAL POLYPHOSPHATE.